Obeplujeme jez, ledaže ho lze projet.

Because obeplujeme comes from the perfective verb obeplout. In Czech, perfective verbs do not normally have a true present meaning; their present-shaped forms usually refer to the future.

So:

• obeplujeme = we will sail/go around
• an imperfective present would be something like obeplouváme = we are sailing around / we sail around

It comes from obeplout:

• plout = to sail, float, move on water
• obe- = around

So obeplout literally means to sail around or go around by water. That is why it fits well with jez (a weir): the sentence is talking about bypassing it by boat or on the water.

Jez is the direct object here, so it is in the accusative case. But jez is a masculine inanimate noun, and for many masculine inanimate nouns, the accusative singular has the same form as the nominative singular.

So:

• nominative: jez
• accusative: jez

That is why there is no visible change.

Because Czech pronouns follow grammatical gender, not real-life animacy in the English sense.

Jez is grammatically masculine, so the accusative pronoun referring back to it is:

• ho = unstressed/clitic form
• jej = fuller, stressed form

So ho here means it, even though in English ho often gets explained first as him.

Normally, no. To is a neuter pronoun/demonstrative, so it does not match jez, which is masculine.

Standard Czech would use:

• ho or jej for jez

So ledaže ho lze projet is the natural standard phrasing.

Because ho is a clitic. Czech clitics usually prefer the second position in their clause.

In the clause:

• ledaže = first element
• ho = clitic in second position

So ledaže ho lze projet is the expected word order.

A version like ledaže lze ho projet is much less natural, because it breaks the usual clitic placement pattern.

Lze is an impersonal word meaning roughly it is possible, one can, or can be.

So:

• ho lze projet = it can be passed through
• more literally: it is possible to go through it

It is fairly common in written or neutral-formal Czech. In more everyday language, you might also hear things like:

• dá se projet
• můžeme ho projet (if the subject is specifically we)

Because lze normally combines with an infinitive.

So the structure is:

• lze + infinitive
• lze projet = it is possible to pass/go through

This is similar to English patterns like it is possible to pass through.

Projet is perfective because the sentence refers to a single successful passage through the weir.

Perfective here emphasizes completing the action:

• projet = to get through / pass through successfully

An imperfective form would suggest repeated, ongoing, or habitual action, which does not fit as well here.

Ledaže means unless or except if. It introduces the exception to what is stated in the main clause.

So the structure is:

• We will go around the weir, unless...

It is correct and natural, but it can sound a bit more written or bookish than some everyday alternatives. Depending on context, speakers might also use expressions such as:

• pokud ne
• jestli ne
• sometimes leda když

But ledaže is a perfectly good standard conjunction.

Because ledaže introduces a subordinate clause, and Czech normally separates subordinate clauses with a comma.

So the punctuation in:

• Obeplujeme jez, ledaže ho lze projet.

is standard Czech punctuation.

Yes. The original ledaže ho lze projet is fairly neat and standard, but a more everyday wording could be something like:

• ledaže se dá projet
• jestli se dá projet
• pokud ho půjde projet

These are not always identical in tone, but they are closer to everyday spoken Czech than lze.